1. Field of the Invention
The present invention relates to the production of bisphenol-A by the reaction of phenol with acetone. More particularly the invention relates to a process wherein the reaction products, especially water, are separated concurrently with the reaction in a distillation column reactor. More particularly the invention relates to a process wherein the water of reaction is removed by stripping with an inert hydrocarbon vapor produced in the reboiler of a distillation column reactor.
2. Related Information
Bisphenol-A is a basic feedstock or intermediate product for the commercial manufacture of various polymers including the polyarylates, polyamides, polyetherimides, polysulfuones and polycarbonates, etc., epoxy resins and modified phenol-formaldehyde resins, etc. Various processes for producing bisphenol-A from the reaction of phenol with acetone in the presence of an acidic ion-exchange resin catalyst have been disclosed in U.S. Pat. Nos. 4,308,404; 4,391,997; 4,400,555; 4,471,154 and 5,087,767.
The method of carrying out catalytic reactions, wherein the components of the reaction system are concurrently separable by distillation, are described variously in U.S. Pat. Nos. 4,215,011; 4,232,177; 4,242,530; 4,250,052; 4,302,356; and 4,307,254 commonly assigned herewith. Briefly, structures which serve as both catalyst site and distillation structure are then disposed in the distillation column reactor. A variety of catalyst structures for this use are disclosed in commonly assigned U.S. Pat. Nos. 4,443,559; 4,536,373; 5,057,468; 5,130,102; 5,133,942; 5,189,001; 5,262,012; 5,266,546; 5,348,710; 5,431,890; and 5,730,843 which are incorporated herein. These structures have been particularly well adapted for use with acidic ion-exchange resins. The method is commonly known as catalytic distillation and has been successfully adapted in various forms for many reactions, including etherification of olefins with alcohols (U.S. Pat. No. 4,302,254), selective hydrogenation (U.S. Pat. No. 6,169,218B1), hydrodesulfurization (U.S. Pat. No. 5,779,883), isomerization (U.S. Pat. No. 6,495,732) and aromatic alkylation (U.S. Pat. No. 4,849,569).
A catalytic distillation column reaction is a benefit first, because the reaction is occurring concurrently with distillation, the initial reaction products and other stream components are removed from the reaction zone as quickly as possible reducing the likelihood of side reactions. Second, because all the components are boiling the temperature of reaction is controlled by the boiling point of the mixture at the system pressure. The heat of reaction simply creates more boil up, but no increase in temperature at a given pressure. As a result, a great deal of control over the rate of reaction and distribution of products can be achieved by regulating the system pressure.
U.S. Pat. No. 5,679,312 discloses producing bisphenol-A by carrying out the reaction by feeding phenol and acetone concurrently downflow in a distillation column reactor having acidic ion exchange resin catalysts held on trays by screens. An inert stripping gas, e.g., nitrogen or argon, is fed in the bottom of the distillation column reactor to aid in removing the water of reaction. With its concurrent feed of the phenol and acetone the patentee gets only about 96% conversion of the acetone. The patentee exhibited a lack of skill and knowledge in regard to catalytic distillation and its areas of significant commercial use as well as being unable to envision how a catalytic distillation system could be used to carry out the reaction of acetone with phenol to produce bisphenol-A.
It is an advantage of the present invention that the catalytic distillation system, with its inherent benefits is employed for the production of bisphenol-A from the condensation reaction of phenol and acetone. It is a further advantage that an inert hydrocarbon serves to remove water of reaction from the reaction system and is easily reused by return to the reaction system. It is a further advantage that substantially all of the acetone is trapped in the reaction zone and near 100% conversion is obtained.